1. Field of Invention
The present invention relates to battery chargers, and more particularly to an auto-controller for battery charger by using thermo-control and current balance technology.
2. Description of Related Arts
Batteries are known that can store electrical energy and play a main role in power tools, toys, portable electrical appliances, and transportation such as vehicles, boats and airplanes. Battery is mainly used to initially start up the engine and supply electrical energy to the accessories such as electronic communication. Therefore, the battery must be in a good condition and in fully charge manner since the non-fully charged battery will be discharged or become so called xe2x80x9cdeadxe2x80x9d when it is not in use for a period of time.
A conventional standard charger is used for charging up the battery wherein the standard charger provides a constant current in, for example, a pulse manner and a fixed duration to the battery as shown in FIGS. 1A, 1B, 2A, and 2B. However, the conventional standard charger has the several drawbacks. The standard charger cannot determine the battery either in a half-full or fully charged condition. The standard charger will apply the relative high current to an empty battery until it is overcharged, which may damage the battery. In other words, no matter what is the condition of the battery, the battery will be considered as an empty battery to be charged by the pulse charger.
Besides, when a relative large current is applied to the battery, heat is generated, which may overheat the battery. Thus, when charging the battery, the electrochemical reaction taken place in the battery releases some poison gas such as sulfur dioxide. The lead plate inside the battery will be coated by the sulfates that reduces the effective of the battery. Such sulfates will function as an internal resistor of the battery for resisting the charging process and the discharging process of the battery. Therefore, the battery will be permanently damaged after a period of time.
Moreover, the effective of the battery will be reduced when the battery is overcharged. When the battery is fully charged, the standard charger still contribute the same amount of current into the battery such that the electrochemical reaction will keep taking place in the battery. Therefore, the reacting substances inside the battery will be reacted and reduced their quantity. The ideal charging process for the battery is to fill up the amount of electrical energy which has been used up in the battery.
A main object of the present invention is to provide an auto-controller for battery charger by using thermo-control and current balance technology for extending a service life span of the battery while being cost effective.
Another object of the present invention is to provide an auto-controller for battery charger by using thermo-control and current balance technology, wherein the battery charger is capable of automatically switching on and off for charging the battery not only in dependence on the occurrence of the current but also when the temperature of the battery is overheated than a control temperature.
Another object of the present invention is to provide an auto-controller for battery charger by using thermo-control and current balance technology, which is responsive to both current overload and thermal overheat. Therefore, the battery charger is effective in operation.
Another object of the present invention is to provide an auto-controller for battery charger by using thermo-control and current balance technology, which can protect the circuit from being burnt. In other words, the current of the battery charger will be cut off by the auto-controller before it is burnt to damage the battery and the battery charger.
Another object of the present invention is to provide an auto-controller for batter charger by using thermo-control and current balance technology, wherein the autocontroller can be incorporated with a conventional battery charger without altering the original structure of the battery charger.
Accordingly, in order to accomplish the above objects, the present invention provides an auto-controller for battery charger by using thermo-control and current balance technology, which comprises:
a resistor having a predetermined resistance for electrically connecting to the battery charger wherein the resistor generates heat when a predetermined current flows through that defines a reference temperature for the battery charger; and
a thermo sensor operatively positioned adjacent to the resistor for detecting the reference temperature and selectively switching the battery charger on and off, whereby when the reference temperature is above a control temperature preset in the thermo sensor, the battery charger is switched off to not function and when the reference temperature is below the control temperature, the battery charger is maintained in a switch-on condition to continuously charge a battery.